The Nutria Nuisance

Louisiana folklore holds that the roly-poly rodent called the nutria (Myocastor coypus), which looks something like a cross between a beaver and a rat, was brought to the bayous of that state, and thence to a good portion of the eastern United States, by the same folks who brought the fiery condiment called Tabasco sauce to a waiting world.

Folklore is not history, and thatâ€™s not quite accurate. But it is true that the president of the McIhenny Company, back in the 1930s, made a curious choice whose implications remain with us today. In 1938, E.A. McIlhenny established a nutria farm on Avery Island, Louisiana, within shouting distance of the factory where the company that bears his family name makes Tabasco sauce. According to company history, McIlhenny bought his stock of nutrias from a farm in New Orleans, so he was not the first to introduce the creature, a native of southern Brazil, Argentina, and Chile, to North America. That dubious honor belongs to another. What is certain, though, is that McIlhenny, for reasons unknown, released an unknown but probably large number of nutrias into the wild from the confines of Avery Island, and from there they fanned out and proliferated.

By 1941, nutria had spread throughout the state and as far west as Port Arthur, Texas. In the next two decades they spread only a little farther down the Texas Gulf Coast, growing not in range but markedly in number, so much so that nutria were blamed for devastating sugarcane and rice harvests for several years running. The blame seems fairly assigned, for nutria, as the biological term has it, are â€œopportunistic feeders,â€ and they eat a quarter of their body weight daily, for an average of about five pounds of vegetation per animalâ€”and rice and sugarcane are fair game in the nutria larder.

In 1958, the federal government instituted wildlife control programs in an effort to curb the spread and absolute number, estimated at more than 20 million, of nutria. Resistance to those programs was widespread in the region, though, since thousands of Texans and Louisianans were were making their living harvesting nutria for their furâ€”and, to a lesser extent, their meat.

The international fur market collapsed in the 1980s, and thereafter few people tried to earn their living from nutria trapping. The nutria population swelled again, and now it began to spread. A quarter-century later, nutria are now found in Canada and 16 American states, with the heaviest concentrations remaining in and around the Gulf Coast, but in significant numbers as far afield as coastal Maryland and Virginia. As their range and number have increased, nutria have crowded the native muskrat out of much of its former territory, and as of 1999 the animal has formally been considered an invasive species.

That designation, in effect, declared open season on nutria. It took some time for that open warfare to make much of a dent in the nutria population, since the market for both nutria fur and meat remains limited, and the federal bounty offered until 2005 amounted to only $4 per animal. Now, nutria in Britain, having escaped from confinement into the wild there in the 1970s, were wholly eradicated the following decade through just such a bounty program; but, as the Louisiana Department of Wildlife and Fisheries notes, the affected area was ten times smaller than that stateâ€™s â€œinfested areas,â€ and the British government actually put trappers on salary rather than rely on a strict program of per-head bounty payment, yielding greater results.

In addition, systematic eradication measures have proved to be difficult to put into wide practice. Zinc phosphide, for instance, was just as likely to poison other animals as it was nutria, while other rodenticides such as strychnine and warfarin travel far along the food chain and are potentially damaging to many species, including humans.

Eradication efforts continue all the same. In Marylandâ€™s Blackwater National Wildlife Refuge, biologists removed invasive nutria in a program that began in 1998 and that terminated in 2004; reported the Washington Post when the program successfully ended, â€œAll it took was two years, $2 million and 15 trappers working in chest-deep muck here on the Eastern Shore. In all, about 8,300 nutria were killed during the eradication, which officials said was planned like a military campaign, using Global Positioning System equipment.â€ Having succeeded in one sector of the Eastern Shore, though, wildlife managers have yet to announce the results of one of the stated goals of the project, which was â€œdesigned to test the hypothesis that nutria can be eradicated on the Delmarva Peninsula,â€ as the Blackwater NWR Nutria Fact Sheet puts it.

The situation is even more critical at the original ground zero of Louisiana, where it was once hoped that a silver lining in the great black cloud that was Hurricane Katrina would be a natural leveling of the nutria population. Many nutria did in fact perish during the storm, as did many other animals, one of Katrinaâ€™s largely untold stories. Yet, as it happens, the nutria have made a comeback; their number is much reduced, granted, but they are wreaking even greater damage on Louisianaâ€™s coastal wetlands than before, since the tupelo-cypress habitat has been badly compromised by the â€œbriningâ€ of the marshes by the storm surge of both Katrina and its successor, Hurricane Rita, and the nutria are effectively making a bad situation worse.

The nutria, of course, are blameless; they did not ask to be set loose on this continent. Yet, given the devastation nutria have wrought on already devastated wetlands and competing animals within their ecological niche, it seems clear that humane eradication is the only course of action. Just how â€œhumaneâ€ current methods are provides a matter for argument, but one odd fact has emerged: the lingering downturn in the economy may prove to be as dark a moment for nutria as it has for so many humans. Reports John Roach for National Geographic, â€œThe 2005 to 2006 trapping season [in Louisiana], which runs from November 20 to March 31, yielded 168,843 nutria tails. The 2009 to 2010 season, by contrast, set a record: 445,963 nutria tails, according to state figures.â€ In hard times, it seems, $5â€”the old per-nutria bounty raised by a dollar after the hurricanes of 2005â€”makes a world of difference.